Most data communications networks today rely heavily on shared-media, packet-based LAN technologies for both access and backbone connections. These networks use bridges and routers to connect multiple LANs into global internets. However, such router-based networks cannot provide the high bandwidth and quality of service required by the latest networking applications and new faster workstations.
Switched networking is a proposed solution intended to provide additional bandwidth and quality of service. In such networks, the physical routers and hubs are replaced by switches and a management system is optionally provided for monitoring the configuration of the switches. The overall goal is to provide a scalable high-performance network where all links between switches can be used concurrently for connections.
One proposal is to establish a VLAN switch domain. A VLAN is a "virtual local area network" of users having full connectivity (sharing broadcast, multicast and unicast messages) independent of any particular physical or geographical location. In other words, users that share a virtual LAN appear to be on a single LAN segment regardless of their actual location. Although the term "VLAN" is widely used as a new method of solving the increasing demand for bandwidth, the effectiveness of existing VLAN systems is wholly dependent on the particular implementation. For example, a VLAN implementation which allows VLAN assignments to end systems, as well as ports, provides a more effective means of VLAN groupings. Other performance-determining characteristics include the manner of resolving unknown destination and broadcast traffic (which consume both network bandwidth and end system CPU bandwidth), the ability to allow transmission out multiple ports, hop-by-hop switching determinations (as opposed to determination of a complete path at the call-originating switch), and whether multi-protocol routers are required to enable transmission between separate VLANs.
Each of these may have an important effect on the total number of connections in trunk switches, the CPU load in the trunk switches, the speed of connection setup, and the scalability of the system, i.e., ability to maintain performance with increasing numbers of end stations and/or switches.